REVISITING DAILY GROWTH OF SOUTHERN BLUEFIN TUNA (THUNNUS MACCOYII) LARVAE FROM THE EASTERN INDIAN OCEAN

Southern bluefin tuna (Thunnus maccoyii, SBT) is a commercially important highly migratory predator whose adults migrate to their only known reproductive hot spot, the nutrient-depleted eastern Indian Ocean (IO).  SBT larvae were collected during January to March 2022 during the peak spawning season aboard the interdisciplinary BLOOFINZ-IO survey (part of the 2nd International IO Expedition). Taxonomic alongside genetic identifications distinguished SBT-2022 from co-occurring scombrid species, and most of the larval tuna were identified as SBT larvae. Somatic variables, otolith microstructure, and daily growth patterns were determined and compared to previous SBT growth estimates for similar sized SBT from 1987 (SBT-1987) as well as to Atlantic bluefin tuna larvae (Thunnus thynnus, ABFT) from the Gulf of Mexico and western Mediterranean Sea. Overall, during the 2022 survey, sea surface temperatures were approximately 2°C warmer, and SBT-2022 grew faster than SBT-1987. In addition, SBT-2022 had larger otoliths and wider increments than in 1987, while otolith growth was strikingly similar to ABFT from the Gulf of Mexico spawning habitat. Complementary studies analyzing environmental conditions and plankton food web structure during the BLOOFINZ-IO survey will be presented in this session and will further our understanding of larval tuna trophodynamics in this climate-sensitive oligotrophic region.

Presentation Preference: Oral

Primary Presenter: Estrella Malca, University of Miami (estrella.malcaphd@gmail.com)

Authors:

Estrella Malca, University of Miami  (estrella.malcaphd@gmail.com)

Ricardo Borrego-Santos, Centro Oceanográfico de Málaga, Instituto Español de Oceanografía (IEO-CSIC)  (rborregosantos@ieo.csic.es)

José María Quintanilla, Centro Oceanográfico de Málaga, Instituto Español de Oceanografía (IEO-CSIC)  (jose.quintanilla@ieo.csic.es)

Carolina Johnstone, Instituto Español de Oceanografía (IEO-CSIC)  (carolina.johnstone@ieo.csic.es)

Rasmus Swalethorp, Scripps Institution of Oceanography, University of California San Diego  (rswalethorp@ucsd.edu)

Isabel Riveiro, Centro Oceanográfico de Vigo, Instituto Español de Oceanografía (IEO-CSIC)  (isabel.riveiro@ieo.csic.es)

Alberto Garcia, Centro Oceanográfico de Málaga, Instituto Español de Oceanografía (IEO-CSIC)  (garaltomar@gmail.com)

David Die, Cooperative Institute for Marine and Atmospheric Studies, University of Miami  (David.die@noaa.gov)

Michael Landry, Scripps Institution of Oceanography, University of California San Diego  (mlandry@ucsd.edu)

Raúl Laiz-Carrión, Centro Oceanográfico de Málaga, Instituto Español de Oceanografía (IEO-CSIC)  (raul.laiz@ieo.csic.es)